Risk Assessment,health Effects,and Intervention Study Of Cadmium Exposure For Human In A Town In Jiangsu Province

Cadmium(Cd)is a heavy metal with accumulation toxicity and can not be degraded in environment,which has been classified as carcinogen.Recently,with the rapid growth of China's economy,mining,smelting and refining,and electroplating industries have been developed a lot,and a large amount of Cd-containing wastewater was discharged into rivers,leading to increasingly serious Cd pollution.Cd may be widely present in air,water,soil,and foods,and ultimately accumulate in human through various pathways and affect human health.Currently,Multi-pathway analysis on health risks of pollutants and the proportions of each pathway is scarce.Only when the proportions of each pathway are clear,can we be able to control risks reasonably and effectively.The Chinese limit of urinary Cd(UCd)is 5 ?g/g creatinine.However,it is still controversial internationally that whether Cd exposure low than 5 ?g/g creatinine is related to adverse health effects,such as hypertension.Domestic research on these topics are insufficient,much less under low exposure levels.Thus,it is very necessary to conduct research on this aspect.In addition,for populations with elevated internal exposure level,research on whether internal exposure is controlled after external exposure has been cut off is very practical.Based on above,this study was conducted in a town in Yixing city,Jiangsu Province.Taking all potential Cd risk sources into consideration,we collected indoor and outdoor air,soils,tap water and well water,home-grown and market-bought food samples and determined Cd concentration in them.We conducted questionnaire surveys for behavior patterns among local population.Besides,we recruited local several smokers from them to experiment smoking process for smoking exposure data.Based on the exposure assessment model recommended by USEPA,average daily intakes(ADI)through water ingestion,water dermal contact,indoor and outdoor air inhalation,soil ingestion,soil dermal contact,food ingestion,and smoking were calculated,and then hazard quotient(HQ)and incremental lifetime cancer risk(ILCR)were estimated.For nonsmokers,the total ADI is 2.56E-03 mg/kg-d,the main pathway being food(mostly Cd-contaminated home-grown rice)ingestion(99.8%).The total HQ is 2.96,and the total ILCR is 1.75E-04,both exceeding the acceptable levels.For smokers,the total ADI is 0.498 mg/kg-d,the main pathway being smoking(99.5%),the total HQ is 52.5,and the total ILCR is 1.07E-03,both far above the acceptable levels.We collected morning urine samples from participants and determined Cd concentrations(adjusted by creatinine)in them to represent internal exposure levels,and determined ?2-microglobulin(BMG)and N-acetyl-?-glucosaminidase(NAG)to represent kidney function effects,and measured their systolic pressures and diastolic pressures.Logistic regression was employed,in which age,gender,body mass index(BMI),smoking status,and diabetes were adjusted.We find that,the average UCd level is 1.26 ?g/g creatinine;hypertension incidence increases with UCd,the odds ratio(OR)being 1.468(95%Cl:1.104,1.953),P=0.008;for female nonsmokers the OR is 1.545(95%CI:1.082,2.206;P=0.017),while for male nonsmokers no significant relationship is found.Diabetes is also significantly related to UCd,the OR being 1.902(95%CI:1.076,3.558;P=0.028).Thus,we conclude that cadmium exposure has an adverse effect on human health even under relatively low level.On the basis of the identification of the main exposure pathway,we recruited a total of 99 nonsmokers from those subjects to participate in an interventional study,in which they were grouped as intervening group,home-grown control group,and market control group according to the sources of rice.The intervention period is 3 months,during when intervening group eat market-bought rice with Cd concentration of 0.005?g/g instead of home-grown rice(Cd:0.40?g/g),while home-grown control group continue eating home-grown rice(Cd:0.29?g/g)and market control group continue eating market-bought rice(Cd:0.02?g/g).After intervention,the average UCd level of intervening group has been significantly decreased from 1.51 ?g/g creatinine to 1.11 ?g/g creatinine(P=0.004),and the average SBP and DBP also have been reduced significantly from 142 to 130(P=0.002)and from 83 to 76(P=0.04),while no significant changes are found in two control groups,demonstrating that this intervention measurement of rice ingestion is an effective way to lower local Cd exposure level and improve human health.